Chap 20 Flashcards
(199 cards)
1
Q
Selective toxicity
A
selectively finding and destroying pathogens without damaging the host
2
Q
Chemotherapy
A
the use of chemicals to treat a disease
3
Q
Antibiotic
A
a substance produced by a microbe that, in small amounts, inhibits another microbe
4
Q
Antimicrobial drugs
A
synthetic substances that interfere with the growth of microbes
5
Q
1928: Fleming discovered penicillin, produced by
A
Penicillium
6
Q
1932: Prontosil red dye used for
A
streptococcal infections
7
Q
1940: First clinical trials of
A
penicillin
8
Q
Today there is a growing problem of
A
antibiotic resistance
9
Q
Bacillus subtilis
A
Bacitracin
10
Q
Paenibacillus polymyxa
A
polymixin
11
Q
More than half our antibiotics are produced by a certain genus of bacteria. What is it?
A
streptomyces
12
Q
Narrow spectrum of microbial activity:
A
drugs that affect a narrow range of microbial types
13
Q
Broad-spectrum antibiotics
A
affect a broad range of gram-positive or gram-negative bacteria
14
Q
Superinfection
A
overgrowth of normal microbiota that is resistant to antibiotics
15
Q
Identify at least one reason why it’s so difficult to target a pathogenic virus without damaging the host’s cells.
A
viruses replicate inside the host cell, utilizing the host’s own cellular machinery to multiply, meaning any attempt to disrupt the virus’s life cycle could also disrupt normal cellular functions, leading to host cell damage.
16
Q
Bactericidal
A
Kill microbes directly
17
Q
Bacteriostatic
A
Prevent microbes from growing
18
Q
________ _________target certain essential functions of the microbe
A
antimicrobial drugs
19
Q
Mechanisms of action include
A
1.inhibiting cell wall synthesis, 2.inhibiting protein synthesis,
3.inhibiting nucleic acid synthesis,
4. injuring the plasma membrane
5.inhibiting synthesis of essential metabolites
20
Q
antimicrobial drug must not interfere with
A
essential functions of the microbe’s host
21
Q
Penicillins prevent the synthesis of
A
peptidoglycan
22
Q
Inhibiting protein synthesis
A
Target bacterial 70S ribosomes
23
Q
Examples of drugs that inhibit protein synthesis
A
Chloramphenicol, erythromycin, streptomycin, tetracyclines
24
Q
Injuring the plasma membrane
A
1.Polypeptide antibiotics change membrane permeability.
- Antifungal drugs combine with membrane sterols
- Ionophores antibiotics allow uncontrolled movement of cations (not for human use).
25
Inhibiting nucleic acid synthesis
Interfere with D N A replication and transcription
26
Inhibiting the synthesis of essential metabolites
Antimetabolites compete with normal substrates for an enzyme.
27
Sulfanilamide competes with
para-aminobenzoic acid (P A B A), stopping the synthesis of folic acid.
28
What cellular function is inhibited by tetracyclines?
protein synthesis
29
Chemotherapeutic Agents
antimicrobial drugs that fight disease by targeting a particular structural difference between human cells and those of the microbe
30
Why is it easier to develop antibacterial drugs?
Bacteria have many such differences
31
Viruses depend on the host's machinery, so there are
fewer differences to target
32
eukaryotic pathogens such as ________& _________ have fewer differences from eukaryotic human cells
fungi & protozoa
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eukaryotic pathogens such as fungi & protozoa have fewer differences from eukaryotic human cells, making it difficult to find drugs that have selective
toxicity against these pathogens.
34
treponema palladium
causes syphilis
35
Synthetic antibiotics vs natural antibiotics
natural- comes from another microbe to be used to fight against
synthetic- not found in nature
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semisynthetic antimicrobial
chemically modified of a natural
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antimicrobial drug
chemical substance that destroys pathogenic microorganisms with minimal damage to host tissues.
38
Chemotherapeutic agents include
chemicals that combat disease in the body.
39
developed the concept of chemotherapy to treat microbial diseases
Paul Ehrlich
40
came into prominence in the 1930s
sulfa drugs
41
discovered the first antibiotic, penicillin, in 1928; its first clinical trials were done in 1940.
Alexander Fleming
42
Most antibiotics are made by
Streptomyces bacteria
43
Antibacterial drugs affect many targets in a
prokaryotic cell.
44
Fungal, protozoan, and helminthic infections are more difficult to treat because
these organisms have eukaryotic cells.
45
Narrow-spectrum drugs affect only a select group of
microbes (gram-positive cells, for example);
45
broad-spectrum drugs
affect a more diverse range of microbes.
46
Which drugs can affect gram-negative cells?
Small, hydrophilic drugs
47
Antimicrobial agents should not cause excessive
harm to normal microbiota.
48
Superinfections occur when
1.a pathogen develops resistance to the drug being used
2.when normally resistant microbiota multiply excessively.
49
Antimicrobials generally act either by
directly killing microorganisms (bactericidal) or by inhibiting their growth (bacteriostatic).
50
Some agents, such as penicillin, inhibit
cell wall synthesis in bacteria.
51
Other agents, such as chloramphenicol, tetracyclines, and streptomycin, inhibit
protein synthesis by acting on 70S ribosomes.
52
Ionophore and polypeptide antibiotics damage
plasma membranes.
53
Some agents inhibit nucleic
acid synthesis.
54
Agents such as sulfanilamide act as
antimetabolites by competitively inhibiting enzyme activity.
55
All penicillins contain a
β-lactam ring.
56
Natural penicillins produced by Penicillium are effective against
gram-positive cocci and spirochetes.
57
Penicillinases (β-lactamases) are bacterial enzymes that destroy
natural penicillins
58
semisynthetic penicillins are resistant to
penicillinases and have a broader spectrum of activity than natural penicillins.
59
Carbapenems
broad-spectrum antibiotics that inhibit cell wall synthesis.
60
The monobactam aztreonam affects only
gram-negative bacteria.
61
Cephalosporins inhibit
cell wall synthesis and are used against penicillin-resistant strains.
62
Polypeptides such as bacitracin inhibit
cell wall synthesis primarily in gram-positive bacteria.
63
Vancomycin inhibits
cell wall synthesis and may be used to kill penicillinase-producing staphylococci.
64
Isoniazid (INH) and ethambutol inhibit
cell wall synthesis in mycobacteria.
65
Chloramphenicol
inhibit protein synthesis at 70S ribosomes.
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aminoglycosides
inhibit protein synthesis at 70S ribosomes.
67
tetracyclines
inhibit protein synthesis at 70S ribosomes.
68
glycylcyclines
inhibit protein synthesis at 70S ribosomes.
69
macrolides
inhibit protein synthesis at 70S ribosomes.
70
streptogramins
inhibit protein synthesis at 70S ribosomes.
71
oxazolidinones
inhibit protein synthesis at 70S ribosomes.
72
pleuromutilins
inhibit protein synthesis at 70S ribosomes.
73
cause damage to plasma membranes.
Lipopeptides polymyxin B and bacitracin
74
Rifamycin inhibits
mRNA synthesis; it’s used to treat tuberculosis.
75
Quinolones and fluoroquinolones inhibit
DNA gyrase.
76
Sulfonamides competitively inhibit
folic acid synthesis.
77
SMZ-TMP competitively inhibits
dihydrofolic acid synthesis.
78
Fungicidal drugs
Polyenes, such as nystatin and amphotericin B,
79
How do Polyenes, such as nystatin and amphotericin B work?
combine with plasma membrane sterols
80
Azoles and allylamines interfere with
with sterol synthesis and are used to treat cutaneous and systemic mycoses.
81
Echinocandins interfere with
fungal cell wall synthesis.
82
The antifungal agent flucytosine is an antimetabolite of
cytosine
83
Griseofulvin interferes with
eukaryotic cell division
84
Griseofulvin is used primarily to treat
skin infections caused by fungi.
85
Entry inhibitors and fusion inhibitors bind to
viral attachment and receptor sites.
86
Nucleoside and nucleotide analogs such as
acyclovir and zidovudine
87
How do antiviral drugs like acyclovir and zidovudine work?
inhibit DNA or RNA synthesis.
88
Inhibitors of viral enzymes prevents
viral assembly and exit.
89
Alpha interferons inhibit
spread of viruses to new cells.
90
Chloroquine used to treat
protozoan infections.
91
artemisinin used to treat
protozoan infections
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quinacrine used to treat
protozoan infections.
93
diiodohydroxyquin used to treat
protozoan infections.
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pentamidine used to treat
protozoan infections
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metronidazole used to treat
protozoan infections.
96
Antihelminthic drugs include
mebendazole, praziquantel, and ivermectin.
97
mebendazole used to treat
anti-helminthic
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praziquantel used to treat
anti-helminthic
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ivermectin used to treat
anti-helminthic
100
Tests are used to determine which chemotherapeutic agent is most likely to
combat a specific pathogen.
101
Tests to guide chemotherapy are used when
susceptibility cannot be predicted or when drug resistance arises.
102
What happens in the kirby-bauer test?
a bacterial culture is inoculated on an agar medium, and filter paper disks impregnated with chemotherapeutic agents are overlaid on the culture.
103
After incubation, the diameter of the zone of inhibition is used to determine
whether the organism is sensitive, intermediate, or resistant to the drug.
104
Minimal inhibitory concentration (MIC)
is the lowest concentration of drug capable of preventing microbial growth; MIC can be estimated using the E test.
105
Explain the broth dilution test
the microorganism is grown in liquid media containing different concentrations of a chemotherapeutic agent
106
minimum bactericidal concentration (MBC).
lowest concentration of a chemotherapeutic agent that kills bacteria
107
Many bacterial diseases, previously treatable with antibiotics, have become
resistant to antibiotics.
108
Superbugs
bacteria that are resistant to several antibiotics.
109
Drug resistance factors are transferred
horizontally between bacteria.
110
Horizontal gene transfer
Transfer of genes between two organisms in the same generation
111
Resistance may be due to
1. enzymatic destruction of a drug
2. prevention of penetration of the drug to its target site
3. cellular or metabolic changes at target sites
4. alteration of the target site
5. rapid efflux of the antibiotic.
112
What can minimize resistance?
The discriminating use of drugs in appropriate concentrations and dosages
113
Antibiotic safety
The risk (e.g., side effects) versus the benefit (e.g., curing an infection) must be evaluated before antibiotics are used.
114
Some combinations of drugs are synergistic
they are more effective when taken together.
115
Some combinations of drugs are antagonistic
when taken together, both drugs become less effective than when taken alone.
116
Future of Chemotherapeutic Agents
New agents include antimicrobial peptides, bacteriocins, and bacteriophages
117
may provide new targets
Virulence factors rather than cell growth factors
118
zone of inhibition
The area of no bacterial growth around an antimicrobial agent in the disk-diffusion method.
119
superinfection
The growth of a pathogen that has developed resistance to an antimicrobial drug being used; the growth of an opportunistic pathogen.
120
selective toxicity
The property of some antimicrobial agents to be toxic for a microorganism and nontoxic for the host.
121
persister cells
Bacterial cells in a population that avoid being killed by antibiotics because they are dormant, not because they are mutants.
122
non-nucleoside inhibitor
A drug that binds with and inhibits the action of the HIV reverse transcriptase enzyme.
123
minimal inhibitory concentration (MIC)
The lowest concentration of a chemotherapeutic agent that will prevent growth of the test microorganisms.
124
minimal bactericidal concentration (MBC)
The lowest concentration of chemotherapeutic agent that will kill test microorganisms.
125
macrolide
An antibiotic that inhibits protein synthesis; for example, erythromycin.
126
ketolide
Semisynthetic macrolide antibiotic; effective against macrolide-resistant bacteria
127
E test
An agar diffusion test to determine antibiotic sensitivity using a plastic strip impregnated with varying concentrations of an antibiotic.
128
disk-diffusion method
An agar-diffusion test to determine microbial susceptibility to chemotherapeutic agents; also called Kirby-Bauer test.
129
chemotherapy
Treatment of disease with chemical substances.
130
carbapenems
Antibiotics that contain a β-lactam antibiotic and cilastatin.
131
A method of determining the minimal inhibitory concentration by using serial dilutions of an antimicrobial drug.
broth dilution test
132
An antibiotic that is effective against a wide range of both gram-positive and gram-negative bacteria
broad-spectrum antibiotic
133
A treatment capable of inhibiting bacterial growth.
bacteriostasis
134
A substance capable of killing bacteria.
bactericide
135
AZOLE
Antifungal agents that interfere with sterol synthesis.
136
antiretroviral
A drug used to treat HIV infection.
137
antibiotic
An antimicrobial agent, usually produced naturally by a bacterium or fungus.
138
antibiogram
Report of antibiotic susceptibility of a bacterium
139
antagonism
Active opposition; (1) When two drugs are less effective than either one alone. (2) Competition among microbes.
140
aminoglycoside
An antibiotic consisting of amino sugars and an aminocyclitol ring; for example, streptomycin.
141
allylamines
Antifungal agents that interfere with sterol synthesis.
142
Who developed the concept of chemotherapy to treat microbial diseases?
Paul Ehrlich
143
What are superbugs?
Bacteria that are resistant to several antibiotics
144
What is the lowest concentration of a drug capable of preventing microbial growth called?
Minimal inhibitory concentration (MIC)
145
Which test uses filter paper disks impregnated with chemotherapeutic agents to determine bacterial sensitivity?
Disk-diffusion test (Kirby-Bauer test)
146
What do nucleoside and nucleotide analogs inhibit?
DNA or RNA synthesis
147
What is the primary use of griseofulvin?
Treat skin infections caused by fungi
148
Which antifungal agent is an antimetabolite of cytosine?
Flucytosine
149
What is the function of azoles and allylamines in antifungal treatment?
Interfere with sterol synthesis
150
Which antifungal drugs combine with plasma membrane sterols and are fungicidal?
Polyenes
151
What do sulfonamides competitively inhibit?
Folic acid synthesis
152
What is phage therapy?
Using bacteriophages to kill bacterial cells
153
What is squalamine?
A steroid with antimicrobial properties isolated from sharks
154
What are magainins?
Antimicrobial peptides from amphibian skin glands
155
What is a promising new avenue of research for developing new antibiotics?
Knowledge of the basic genetic structure of microbes
156
What percentage of bacterial species found in nature are incapable of being grown on conventional laboratory media?
Over 99%
157
What makes gram-negative bacteria resistant to most antibiotics?
Their cell wall
158
Why do most drugs fail when tested against dormant cells?
They are tested against exponentially growing pathogens
159
What is one potential target for new antimicrobial drugs?
Sequestering iron
160
Why is there a concern about a post-antibiotic era?
Pathogens are developing resistance to current chemotherapeutic agents
161
What is a new approach to controlling pathogens mentioned in the text?
Targeting their virulence factors
162
How does tetracycline interfere with the action of penicillin?
Tetracycline stops the growth of bacteria, which interferes with penicillin's requirement for bacterial growth
163
What is an example of antagonism in drug treatment?
Penicillin and tetracycline
164
What is antagonism in the context of drug interactions?
The simultaneous use of two drugs is less effective than when either drug is used alone
165
How does penicillin enhance the effectiveness of streptomycin in treating bacterial endocarditis?
Penicillin damages bacterial cell walls, making it easier for streptomycin to enter
166
What is an example of synergism in drug treatment?
Penicillin and streptomycin
167
What is synergism in the context of drug interactions?
The chemotherapeutic effect of two drugs given simultaneously is greater than the effect of either given alone
168
What is a possible hypersensitivity reaction to penicillins?
Allergic reaction
169
What should a pregnant woman consider when taking antibiotics?
Only take antibiotics classified by the FDA as presenting no evidence of risk to the fetus
170
What kind of damage can potentially be caused by serious side effects of antibiotics?
Liver or kidney damage
171
Which antibiotic is known to neutralize the effectiveness of contraceptive pills?
Rifampin
172
What is the term for assessing the risks against the benefits of administering a drug?
Therapeutic index
173
What is the recommended practice for patients to prevent antibiotic resistance?
Finish the full regimen of their antibiotic prescriptions
174
What is the role of β-lactamase enzymes in antibiotic resistance?
They hydrolyze the β-lactam ring of antibiotics
175
What is a common method to prevent the formation of antibiotic aerosols during injection?
Inserting the needle into sterile cotton to expel air bubbles
176
Which structure in bacteria restricts absorption of many molecules, contributing to antibiotic resistance?
Porins
177
What is one major mechanism by which bacteria become resistant to antibiotics?
Enzymatic destruction or inactivation of the drug
178
What practice in the developed world contributes significantly to antibiotic resistance?
Using antibiotics in animal feeds to promote growth
179
What percentage of antibiotics in rural Bangladesh were prescribed by a physician?
8%
180
What is the primary cause of antibiotic misuse in less-developed areas?
Antibiotics can be purchased without prescriptions
181
How are antibiotic resistance genes commonly spread among bacteria?
Horizontally by conjugation or transduction
182
What term is used for bacteria that survive antibiotic treatment due to genetic characteristics?
Persister cells
183
What is the purpose of antibiograms prepared by hospital personnel?
To record the susceptibility of organisms encountered clinically
184
What additional information can a broth dilution test provide that the diffusion method cannot?
Whether a drug is bactericidal
185
What is determined by making a sequence of decreasing concentrations of the drug in a broth?
Minimal inhibitory concentration (MIC)
186
187
An antimicrobial drug that inhibits peptidoglycan synthesis is most likely to be effective against
Gram positive bacteria
188
Bacterial infections are easier to treat using chemotherapy because
Bacteria are prokaryotic, many differences between cell types. Affect prokaryotic cells, but not human cells.
189
When do Superinfections occur
1.Pathogen develops resistance to the drug being used
2.Normally resistant microbiota multiply excessively
190
A disadvantage of using broad spectrum antibiotics for treating bacterial infections is the potential for
Superinfection
191
Clindamycin binds to which ribosomal subunit to inhibit translocation?
50s
192
Clindamycin stops
Translation in prokaryotes
193
Which antibiotic has noted association Clostridium difficile associated diarrhea?
Clindamycin
194
Which antibiotic: It's effectiveness against anaerobes has led to its use in the treatment of acne
Clindamycin
195
Sulfa drugs block the cell's ability to
synthesize essential metabolites
196
Anthelmintic drug that causes paralysis of the worm
Ivermectin
197
Results in paralysis and death of the helminth without affecting mammalian host
Ivermectin
198
Example of broad spectrum antihelmintic
Ivermectin
